No tool will write good CSS selectors for you, just like no tool can write good code for you. Yes, you can generate code from templates, but only for the most repetitive of coding tasks. CSS is more art than science, and as such "auto-generation" will not yield good results.
Writing good, clean, lean, maintainable CSS requires an intimate knowledge of the HTML markup, the style & layout that you are trying to achieve, and the skill of identifying patterns across the whole site, such as font, color, h1 headings, presentation of tabular data etc., which are re-used.
Even writing your own script will not produce good CSS. The best you could hope for is to extract all those inline styles, replace them with a unique id or class, and dump them all into a css file. I don't actually see a lot of benefit in that exercise. You actually end up with more code to maintain because of all the extra id's or classes that you will create.
You will not gain consistency of appearance throughout your site from the above exercise, unless you start to consolidate all those unique id's or classes into fewer, more re-used ones, and this is a task best done by hand, not automation anyway. Page load times may improve due to browser caching of the css stylesheet, but thats about all you gain.
Sorry if I've strayed a bit from your question, but your site sounds like it is crying out for you to re-write your CSS from scratch.
Check out CSS Zen Garden for inspiration on what CSS can do, and examples of beautiful CSS, and be inpired!